The present invention relates generally to a cable tie installation tool, and more specifically, to such a tool having an ergonomic trigger mechanism.
As is well known to those skilled in the art, cable ties (or straps) are used to bundle or secure a group of articles such as electrical wires or cables. Cable ties of conventional construction include a cable tie head and an elongate tail extending therefrom. The tail is wrapped around a bundle of articles and thereafter inserted through a passage in the head. The head of the cable tie typically supports a locking element which extends into the head passage allowing the tail to be inserted through the passage but preventing retraction of the tail through the passage in the head. Two longitudinally separated portions of the tail are thereby secured to the head to define a loop for holding together the group of articles.
In practice, the installer manually places the tie about the articles to be bundled, inserts the tail through the head passage and then manually tightens the tie about the bundle. At this point, a cable tie installation tool is used to tension the cable tie. One type of such a cable tie installation tool includes a housing which is generally pistol-shaped where the housing has a barrel into which the tail may be inserted for application of the tension. The housing has a grip which depends from the barrel. The tool includes a trigger mechanism having a trigger member located under the barrel and in front of the grip. The trigger member is elongate and in generally depending relation relative to the barrel such that, when the heel of the hand of a user is placed against the grip such that the fingers of the user's hand extend forwardly, the fingers may encircle the forward surface of the trigger member. Forcibly drawing the fingers toward the heel of the hand, i.e., squeezing the trigger member and grip, causes the trigger member to be displaced toward the grip. The trigger mechanism extends into the housing and is able to grasp the tail, and to apply the predetermined tension thereto in proportion to the drawing or squeezing force applied to the trigger member.
The trigger member of such a cable tie installation tool is typically pivotally mounted adjacent to the barrel such that, when the trigger member is at the maximum displacement from the grip, the trigger member is inclined relative to the barrel and grip. This inclination results in the distance between the trigger member and grip being smallest adjacent to the barrel and increasing in the direction away from the barrel. This inclination is maximum when the trigger member is open prior to any squeezing thereof. The squeezing of the trigger member causes the trigger member to pivot toward the grip causing the angle between the trigger member and the grip to close.
The inclination of the trigger member prior to the squeezing thereof has ergonomic disadvantages. One such disadvantage is that the smaller fingers of the hand (i.e., the smallest and ring fingers) are more distant from the pivotal connection of the trigger member as compared to the larger fingers (i.e., the index and middle fingers). This relative distance is significant because the squeezing force applied to the trigger member is increasingly multiplied as the squeezing force is more distant from the pivotal connection. The squeezing force is translated, via the trigger mechanism, to the tension force applied to the cable tie.
Since the smaller fingers typically have less strength than the larger fingers, the force multiplication generated by the pivoting of the trigger member is less than it would be if the larger fingers were farther from the pivotal connection. If a substantial squeezing force is required to be applied to the trigger member, e.g., a substantial tension is required in the cable tie, then the smaller fingers may become strained. Alternatively, to generate such a substantial tension, the inclination of the trigger member may be increased to make greater the leverage of the trigger member. However, such an increase in the inclination would require the smaller fingers to extend farther to initially grasp the trigger member. This would normally be difficult due to the limited length of such fingers.